This is the long version of a study published previously as a short research letter by JAMA Pediatrics, but retracted (Walach, H., Weikl, R., Prentice, J., Diemer, A., Traindl, H., Kappes, A., & Hockertz, S. (2021). Retracted: Experimental assessment of carbon dioxide content in inhaled air with or without face masks in healthy children: A randomized clinical trial. JAMA Pediatrics. doi:10.1001/jamapediatrics.2021.2659). In our view, the retraction was not warranted and violated the ethical code of publishing, which knows three reasons for retractions, none of which was present: fabricated or wrong data, wrong analysis, plagiarism. The texts of our comments and rebuttals were not published by the journal, but can be found on Retraction Watch (https://retractionwatch.com/2021/07/16/jama-journal-retracts-paper- on-masks-for-children/). The “additional scientific review” JAMA Pediatrics mentions in the retraction was not sent to us despite our asking for it twice.

We therefore publish here the full text, as it was submitted to another peer-reviewed journal, where it is currently under review. The text might change as a consequence of peer-review.